The field of the present disclosure relates to data readers such as scanners, optical code reading devices, and electronic tag (e.g., Radio Frequency Identification “RFID”) readers. In the following description, the focus is on barcode reading, but the present disclosure is generally applicable to other types of symbol reading, object identification, or electronic tag reading.
A barcode label comprises a series of parallel dark bars of varying widths with intervening light spaces, also of varying widths. The information encoded in the barcode is represented by the specific sequence of bar and space widths, the precise nature of this representation depending on which particular barcode symbology is in use. Typical methods for reading barcodes comprise generation of an electronic signal wherein a signal voltage alternates between two preset voltage levels, one representing a dark bar and the other representing a light space. The temporal widths of these alternating pulses of high and low voltage levels correspond to the spatial widths of the bars and spaces. It is this temporal sequence of alternating voltage pulses of varying widths which is presented to an electronic decoding apparatus for decoding.
Bar codes are just one example of the many types of optical codes in use today. The most common bar codes are one-dimensional or linear optical codes, such as the UPC code or Code 39 bar code, where the information is encoded in one direction—the direction perpendicular to the bars and spaces. Higher-dimensional optical codes, such as, two-dimensional matrix codes (e.g., MaxiCode) or stacked codes (e.g., PDF 417), which are also sometimes referred to as “bar codes,” are also used for various purposes.
One common type of barcode reader is a spot scanner in which a source of illumination is moved (i.e., scanned) across the barcode while a photodetector monitors the reflected or backscattered light. The illumination source in a spot scanner is typically a laser, but may comprise a coherent light source, such as a laser or laser diode, or a non-coherent light source, such as a light emitting diode (LED). A laser illumination source may offer advantages of higher intensity illumination which may allow barcodes to be read over a larger range of distances from the barcode scanner, i.e., having a large depth of field, and under a wider range of background illumination conditions.
The reading spot of the scanner may be manually moved across the barcode, this type of reader being typically referred to as a wand. Alternately, the spot may be automatically moved or scanned across the barcode in a controlled pattern. The scanning mechanism may comprise a rotating mirror facet wheel, an oscillating mirror, or other suitable mechanism for pivotally moving/scanning the illumination beam. The path followed by the scanned illumination beam is referred to as a scan line. Typically, an individual scan line must extend across the barcode for the barcode to be successfully read unless specialized piecing/assembly software, known as stitching, or electronics are utilized to combine partial scan segments. In addition to the scan engine, barcode scanner may also employ a set of scan pattern generating optics such as pattern mirrors to produce a multiplicity of scan lines in various directions from the scanner and at varying orientations, thereby allowing barcodes to be read over a large angular field of view and over a wide range of orientations, that is a multi-dimensional scan pattern.
Another type of data reader is the imaging reader such as a CCD (charge coupled device) or CMOS (complimentary metal oxide semiconductor) in which an entire line of the barcode image or a two-dimensional image of a scan region is focused onto a detector array. The imaging reader typically includes a light source to illuminate the barcode to provide the required signal response. For the purpose of this description, the word “scanner” may be referred to data readers both of the spot scanner type and the imaging type.
Yet another type of data reader is an electronic tag reader such as an RFID reader. The RFID reader has an antenna that emits radio waves and the RFID tag responds by sending back its data which in turn is captured by a receiver in the reader.
In relation to data reader operation/function, one way in classifying how data readers are operated is via the two modes: (1) handheld (or portable) and (2) fixed (or hands-free). In the fixed or hands-free mode of operation, the data reader is fixed/stationary while the barcoded objects or other objects to be read are passed through or held within a larger read volume. In the portable or handheld mode of operation, the data reader is moved or otherwise aimed at the barcode label or electronic tag to be read.
In a combined function data reader which is to be used in both fixed and handheld modes of operation, it is desirable for the combined function data reader to have different functional characteristics when operating either of the fixed or handheld modes. Previously combined handheld/fixed data readers have employed various mechanisms for detecting when the reader is being switched between handheld and fixed modes of operation. For example, in a fixed mode of operation, a barcode reader may generate an omnidirectional scan pattern projected into a scan field but when picked up and used in a handheld mode, switches to a single line laser scan pattern by operation of manually actuable trigger on the reader housing.
Various methods/systems for switching the data reader as between modes have been proposed. For example, the base of the unit may include a mechanical or magnetic bottom switch, such as a contact or pressure switch, that detects/actuates when the reader is lifted off of a surface or removed from a stand. In another example, such as U.S. Pat. No. 4,766,297, a scanner may include an optical sensor that senses when the scanner is removed from the stand and then switches to handheld mode. In yet another example, U.S. Pat. No. 7,243,850 discloses, among other things, a combination handheld/fixed scanner that includes a motion sensor which senses that the unit has been picked up by the operator, and when the sensor detects motion, it is switched from the fixed mode of operation to the handheld mode of operation.
Thus though there have been various methods proposed for switching the data reader as between modes, the present inventors have determined that improved methodologies are desirable.